1. Field of Invention
At least one embodiment of the present invention relates generally to control systems and methods for generating a signal, and more specifically, for generating an output signal having a frequency that is a multiple of a frequency of the input signal.
2. Discussion of Related Art
Digital circuits and their components are driven by clock signals that oscillate between a high state and a low state at a given frequency. Clock signals can be used to synchronize various system components, and to direct the operation of one or more circuits within the system. A clock signal can operate as a source for many different circuits that form part of a device, such as a computer or mobile telephone handset. However, various circuits or their components within such devices can require different frequencies in order to operate properly or more efficiently, and therefore, a single clock signal operating at a fixed frequency may be insufficient to drive varying circuits and to meet their differing requirements.
Mobile telephone handsets and other electronic devices require multiple clock signals at different frequencies. These devices are used in communication systems or telecommunication networks such as Global System for Mobile Communications (GSM), General Packet Radio Service (GPRS) or Enhanced Data Rate for GSM Evolution (EDGE) networks. Existing ways of changing or adjusting a clock signal frequency result in signals with inaccurate and shifting duty cycles that are difficult to control. This is in part because existing techniques for adjusting clock signal frequency are susceptible to operationally significant temperature and voltage fluctuations. In addition, conventional frequency multipliers have high current and power requirements, and are physically large circuits, making compact and efficient placement on computer chips impractical.